More particularly, the invention relates to such a runner that comprises firstly first and second rails mounted to slide relative to each other in a longitudinal direction, and secondly a locking mechanism for preventing said first and second rails from moving relative to each other, the locking mechanism comprising:
a longitudinal succession of catches carried by the first rail;
a main latch which is provided with a series of teeth and which is connected to the second rail, said main latch being mounted substantially to pivot about a first pivot axis between a locked position in which the series of teeth co-operates with the catches on the first rail so as to prevent the first and second rails from moving relative to each other, and an unlocked position in which the series of teeth does not co-operate with the catches on the first rail so as to enable the first and second rails to move longitudinally relative to each other; and
control means comprising a control member that can be moved between a locking position and an unlocking position so as to cause the main latch to pivot from the locked position towards the unlocked position.
When the front or the rear of the vehicle is subjected to an impact, the runners that connect the floor of the vehicle to the unit constituted by the seat and its occupant must thus be adapted to absorb the longitudinal impact in order to hold said seat and its occupant.
The impact is absorbed by means of the main latch, and more exactly by means of its series of teeth that co-operate with the catches on the first rail.
That type of latch is described in particular in Document FR-A-2 736 311.
Unfortunately, the main latch which is mounted to pivot on the second rail can contain only a small number of teeth, e.g. three teeth, serving to co-operate with the catches on the first rail. It is not possible to increase the number of teeth in the series of teeth on the main latch without also increasing the angle through which said main latch pivots between its locked position and its unlocked position, so as to retract all of the teeth of the series of teeth from the catches on the first rail. The angle through which the main latch can pivot is limited by the space defined by the first and second rails. Thus, the number of teeth in the series of teeth on the main latch that are used for absorbing impacts is small, which might give rise to its teeth being deformed or torn off when the vehicle is subjected to a violent impact.